There are two primary switching architectures that enable telecommunications between two points in a digital communication system, namely, circuit-switching technology and packet-switching technology. Circuit-switching technology employs dedicated lines or channels to transmit data between the two points, as in public switched telephone networks (PSTN). Packet-switching technology, on the other hand, employs a “virtual” channel, often referred to as a link, to establish communications between the two points. The virtual communication link is typically shared by multiple communication processes simultaneously and is only utilized when data is to be transmitted. Since the differing performance requirements for voice transmission and data transmission impose different design priorities, historical development of voice communication systems, such as telephone systems, has relied on circuit-switching technology. Alternatively, data communication systems, such as local area networks (LANs), wide area networks (WANs) and the Internet, have relied primarily on packet-switching technology.
In the context of a digital voice communication system, a digital signal level 0 (DS0) channel having a 64 kilobits per second (Kbps) capacity is typically employed to convey voice data between two points in the system. A digital signal level 1 (DS1) link often carries voice interface connections on a private branch exchange (PBX). Each DS1 link has either 24 DS0 channels framed together, in the case of a T-carrier 1 (T1) link with a 1.544 megabits per second (Mbps) data rate, or 32 DS0 channels framed together, in the case of an E-carrier 1 (E1) link with a 2.048 Mbps data rate, so that each DS0 timeslot can be assigned to a different type of trunk group, if desired. Each DS0 channel forms a timeslot in a given frame of the DS1 link. Frame relaying standards specifying frame formats and procedures for the transfer of data using frame relaying networks are set forth, for example, in the documents ITU Recommendation Q.922, ISDN Data Link Layer Specification for Frame Mode Bearer Services, ITU, Geneva, 1992, and ITU Recommendation Q.933, ISDN Signaling Specification for Frame Mode Bearer Services, ITU, Geneva, 1995, which are incorporated by reference herein. Additional frame relaying standards, including, for example, ANSI T1.403, Carrier to Customer Installation DS1 Metallic Interface, American National Standards Institute, New York, 1995, ANSI T1.410-1992, Carrier-to-Customer Metallic Interface—Digital Data at 64 Kbit/s and Subrates, American National Standards Institute, New York, 1992, ANSI T1.107-1995, Digital hierarchy—Formats specifications, American National Standards Institute, New York, 1995, ITU Recommendation G.703, Physical/electrical Characteristics of Hierarchical Digital interfaces, ITU, Geneva, 1988, and ITU Recommendation G.704, Synchronous Frame Structures used at Primary and Secondary Hierarchical Levels, ITU, Geneva, 1991, are also incorporated by reference herein.
If the DS0 channels associated with a given DS1 link were identical to one another, delays associated with the DS0 timeslots in the DS1 link would also be substantially the same relative to one another. However, this is rarely the case in a digital communication system. Rather, the delays of the DS0 timeslots in a given DS1 link can vary widely depending on certain characteristics of the corresponding DS0 channels, such as, for example, the distance between two nodes coupled by a given channel. Unfortunately, when a DS1 link carries temporal data, as in the case of digital voice communications, it is critical to be able to have various frames of data in the DS0 timeslots arrive in a specified order, so that the received data can be reconstructed in its proper sequence. While it may be known to adjust the overall delay on a given link, thereby affecting the delays of all DS0 channels to the same degree, there is presently no known methodology for selectively controlling the delay of each individual timeslot on a particular link, so as to guarantee that the frames of data carried by the link are received in the proper sequence.
Accordingly, there exists a need for a methodology for individually controlling the delay of one or more timeslots on a data transport link that does not suffer from one or more of the problems exhibited by conventional methodologies.